re: Why are bassists looked down on

There's a lot of reasons:
1. Bass is the instrument that requires the least amount of talent to play passably in a band playing fairly simple music.
2. Bassists are often socially awkward.
3. Nothing about bass is "sexy". They're generally always a role player, never the star.

This creates the perception that bassists aren't valued. While it's a funny joke, a meme, and a truth among female groupies, a great bassist is worth its weight in gold. They are hard to come by and can really add a ton of value to a band's sound. They are also very much so in demand and hard to keep. It is much easier to replace a drummer or a lead guitar player than it is to replace a really talented bassist.